import numpy as np
eV = 1.6e-19
KeV = 1000 * eV
MeV = 1e6 * eV
GeV = 1e9 * eV
c_light = 3e8
me = 9.1e-31
mc2 = me * c_light * c_light
hbar = 6.626e-34 /(2.0 * np.pi)
r0 = 2.818e-15
alpha = 1/137.0
lambdah = hbar / (me*c_light)
lambdacompton = lambdah
mb = 1e-31

rhogold = 19.3
na = 6.02e23
ag = 197
ngold = rhogold * na / ag * 1e6
epsilon_0 = 8.854187187e-12
mu_0 = 1.256637061e-6


